Simultaneously enhanced toughness and strain tolerance of SiC-based ceramic composite by in-situ formation of VB2 particles

Abstract

SiC-30vol%VB2 ceramic composite was pressureless densified at 2150°C with excess B4C and C as sintering aids after in-situ formation of VB2 in SiC matrix. The sintered bulk gained a considerably high fracture toughness of 7.0±0.4MPam1/2, which was ∼2.4 times as high as that of the monolithic SiC ceramic, owing to the existences of weak heterophase boundaries, thermal residual stresses and microcracks. Meanwhile, since the VB2 particle has a lower elastic modulus than SiC and significantly suppressed the grain growth of SiC, the composite exhibited a high flexural strength of 458±36MPa and a relatively low Young’s modulus of 356±6GPa, resulting in an increase of ∼59.3% in mechanical strain tolerance (1.29×10−3) compared with that of single-phase SiC ceramic. Besides, the residual stresses and microcracks also induced a lower-than-expected Vickers hardness of 20.8±0.5GPa in the composite.